1. Field of the Invention
The invention relates to a method of and a device for determining the type of a cassette in a magnetic-tape recording and/or reproducing apparatus, for example, a video recorder of the helical-scan type, so as to enable the total playing time of a tape accommodated in the cassette to be determined.
It is to be noted here that the invention is not only of interest for video recorders of the helical-scan type, but is suitable in magnetic-tape recording and/or reproducing apparatuses in general, i.e. also those of the linear type.
2. Description of the Related Art
A method of and a device for determining the type of a cassette inserted in a video recorder is known, for example from DE-PS 30 49 296. In that case, the sum of revolution times of the take-up spool and the supply spool of the inserted cassette is measured to determine the cassette type, so that the total playing time, the residual playing time and the playing time of the tape already used can be calculated.
In addition, EP 580,253 A2 (PHD 92-092) and the corresponding U.S. patent application Ser. No. 08/96,581, filed Jul. 21, 1993 disclose a method and a device in which two measurements are performed to determine the total playing time, where, in a first measurement, the tape is wound briefly in a threaded-out condition and, in a second measurement, the tape is moved into a threaded-in condition. In the two measurements, the number of pulses produced by the reel discs, which are coupled to the take-up reel and the supply reel of a cassette inserted into an apparatus, are used to determine the total playing time of the tape.